BIFFwriter.php

<?php
/*
*  Module written/ported by Xavier Noguer <xnoguer@rezebra.com>
*
*  The majority of this is _NOT_ my code.  I simply ported it from the
*  PERL Spreadsheet::WriteExcel module.
*
*  The author of the Spreadsheet::WriteExcel module is John McNamara 
*  <jmcnamara@cpan.org>
*
*  I _DO_ maintain this code, and John McNamara has nothing to do with the
*  porting of this code to PHP.  Any questions directly related to this
*  class library should be directed to me.
*
*  License Information:
*
*    Spreadsheet::WriteExcel:  A library for generating Excel Spreadsheets
*    Copyright (C) 2002 Xavier Noguer xnoguer@rezebra.com
*
*    This library is free software; you can redistribute it and/or
*    modify it under the terms of the GNU Lesser General Public
*    License as published by the Free Software Foundation; either
*    version 2.1 of the License, or (at your option) any later version.
*
*    This library is distributed in the hope that it will be useful,
*    but WITHOUT ANY WARRANTY; without even the implied warranty of
*    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
*    Lesser General Public License for more details.
*
*    You should have received a copy of the GNU Lesser General Public
*    License along with this library; if not, write to the Free Software
*    Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
*/

/**
* Class for writing Excel BIFF records.
* 
* From "MICROSOFT EXCEL BINARY FILE FORMAT" by Mark O'Brien (Microsoft Corporation):
*
* BIFF (BInary File Format) is the file format in which Excel documents are 
* saved on disk.  A BIFF file is a complete description of an Excel document.
* BIFF files consist of sequences of variable-length records. There are many 
* different types of BIFF records.  For example, one record type describes a 
* formula entered into a cell; one describes the size and location of a 
* window into a document; another describes a picture format.
*
* @author Xavier Noguer <xnoguer@rezebra.com>
* @package Spreadsheet_WriteExcel
*/

class BIFFWriter
{
    var $_BIFF_version = 0x0500;

/**
* Constructor
*
* @access public
*/
    function BIFFwriter()
    {
        // The byte order of this architecture. 0 => little endian, 1 => big endian
        $this->_byte_order = '';
        // The string containing the data of the BIFF stream
        $this->_data       = '';
        // Should be the same as strlen($this->_data)
        $this->_datasize   = 0;
        // The maximun length for a BIFF record. See _add_continue()
        $this->_limit      = 2080;   
        // Set the byte order
        $this->_set_byte_order();
    }

/**
* Determine the byte order and store it as class data to avoid
* recalculating it for each call to new().
*
* @access private
*/
    function _set_byte_order()
    {
        if ($this->_byte_order == '')
        {
            // Check if "pack" gives the required IEEE 64bit float
            $teststr = pack("d", 1.2345);
            $number  = pack("C8", 0x8D, 0x97, 0x6E, 0x12, 0x83, 0xC0, 0xF3, 0x3F);
            if ($number == $teststr) {
                $byte_order = 0;    // Little Endian
            }
            elseif ($number == strrev($teststr)){
                $byte_order = 1;    // Big Endian
            }
            else {
                // Give up. I'll fix this in a later version.
                die("Required floating point format not supported ".
                    "on this platform. See the portability section ".
                    "of the documentation."
                   );
            }
        }
        $this->_byte_order = $byte_order;
    }

/**
* General storage function
*
* @param string $data binary data to prepend
* @access private
*/
    function _prepend($data)
    {
        if (strlen($data) > $this->_limit) {
            $data = $this->_add_continue($data);
        }
        $this->_data      = $data.$this->_data;
        $this->_datasize += strlen($data);
    }

/**
* General storage function
*
* @param string $data binary data to append
* @access private
*/
    function _append($data)
    {
        if (strlen($data) > $this->_limit) {
            $data = $this->_add_continue($data);
        }
        $this->_data      = $this->_data.$data;
        $this->_datasize += strlen($data);
    }

/**
* Writes Excel BOF record to indicate the beginning of a stream or
* sub-stream in the BIFF file.
*
* @param  integer $type type of BIFF file to write: 0x0005 Workbook, 0x0010 Worksheet.
* @access private
*/
    function _store_bof($type)
    {
        $record  = 0x0809;        // Record identifier
        $length  = 0x0008;        // Number of bytes to follow
        $version = $this->_BIFF_version;
   
        // According to the SDK $build and $year should be set to zero.
        // However, this throws a warning in Excel 5. So, use these
        // magic numbers.
        $build   = 0x096C;
        $year    = 0x07C9;
   
        $header  = pack("vv",   $record, $length);
        $data    = pack("vvvv", $version, $type, $build, $year);
        $this->_prepend($header.$data);
    }

/**
* Writes Excel EOF record to indicate the end of a BIFF stream.
*
* @access private
*/
    function _store_eof() 
    {
        $record    = 0x000A;   // Record identifier
        $length    = 0x0000;   // Number of bytes to follow
        $header    = pack("vv", $record, $length);
        $this->_append($header);
    }

/**
* Excel limits the size of BIFF records. In Excel 5 the limit is 2084 bytes. In
* Excel 97 the limit is 8228 bytes. Records that are longer than these limits
* must be split up into CONTINUE blocks.
*
* This function takes a long BIFF record and inserts CONTINUE records as
* necessary.
*
* @param  string  $data The original binary data to be written
* @return string        A very convenient string of continue blocks
* @access private
*/
    function _add_continue($data)
    {
        $limit      = $this->_limit;
        $record     = 0x003C;         // Record identifier
 
        // The first 2080/8224 bytes remain intact. However, we have to change
        // the length field of the record.
        $tmp = substr($data, 0, 2).pack("v", $limit-4).substr($data, 4, $limit - 4);
        
        $header = pack("vv", $record, $limit);  // Headers for continue records
 
        // Retrieve chunks of 2080/8224 bytes +4 for the header.
        for($i = $limit; $i < strlen($data) - $limit; $i += $limit)
        {
            $tmp .= $header;
            $tmp .= substr($data, $i, $limit);
        }

        // Retrieve the last chunk of data
        $header  = pack("vv", $record, strlen($data) - $i);
        $tmp    .= $header;
        $tmp    .= substr($data,$i,strlen($data) - $i);
 
        return($tmp);
    }
}
?>